curvature versus slope
  n = 166643 
  X=0, Y = 21.54 +/- 19.21 
  Weighted least-squares fit:  Y = 53.8 + 1.928 X  + -0.02058 X**2 

slope versus dZ, curvature < 5
  n = 16312 

  Weighted least-squares fit:  Y = 23.6 + 0.278 X  + 0.00058 X**2 
     at X = 100, Y = 57.1 
     effective RMSE xy = 81.8 

slope versus dZ, curvature < 15
  n = 31204 

  Weighted least-squares fit:  Y = 23.0 + 0.372 X  + 0.00006 X**2 

curvature versus dZ, slope < 10
  n = 13829 
  X=0, Y = 25.78 +/- 12.56 
  Weighted least-squares fit:  Y = 24.8 + 0.564 X  + 0.07901 X**2 


Number of samples 169890
Max dz = 900
Mean dz = 59
RMS dz = 98.1121806913
100cm = 83.3692389193 percentile value of dz